As is well known, an ink-jet recording method is one method of printing methods and is utilized in various fields of image formation because multi-color fine images can be formed. For example, the ink-jet recording method is used for formation of a picture element area in the production of a separation rib (so-called “partition pattern”) of a color filter and a black matrix of a liquid crystal display device.
For example, Japanese Unexamined Patent Publication (Kokai) No. 6-347637 discloses a method of printing a color pattern between the space of partition patterns (black matrix) containing fluorine-based water and oil repellency agents, characterized in that printing is conducted by using ink having a specific surface tension. In the case of this printing method, the partition pattern can be produced by known methods such as gravure printing method, photoresist method, thermal transfer method and the like. Japanese Unexamined Patent Publication (Kokai) No. 7-35915 discloses a color filter comprising a transparent substrate, a plurality of picture elements formed at a predetermined position of the transparent substrate, and a light shielding black matrix between the space of the picture elements, characterized in that the light shielding black matrix is a black resin layer containing a fluorine-containing compound and/or a silicon-containing compound. In the case of this color filter, the black matrix can be formed by using a black photosensitive resin composition as a starting material according to a photoresist method and the following formation of the picture elements can be conducted by a printing method or an ink-jet recording method.
The reason why the black matrix is formed from the black resin layer containing the fluorine-containing compound and/or silicon-containing compound in the above-described color filter is as follows. That is, when picture elements are formed by the ink-jet recording method, droplets of ink are ejected and dropped from a head of an ink-jet printer to an opening portion (picture element area) surrounded by the black matrix. In that case, ink having very low viscosity and small surface tension must be used so as to accurately eject small droplets of ink at high speed and to quickly spread them in a uniform thickness in the opening portion. Therefore, it becomes necessary to impart ink repellency (water repellency and oil repellency) to the black matrix itself for the purpose of preventing color mixture caused by leakage of ink from the black matrix. Suitable material includes the above-described fluorine-containing compound and silicon-containing compound.
By the way, a conventional method of forming a black matrix has several problems. For example, in case where the black matrix is formed from the above-described black photosensitive resin composition or a similar photosensitive composition prepared by dispersing black pigments, dyes or metal powders in a resin for the purpose of imparting a light shielding property according to a photoresist method, it is essential to conduct various treatments such as coating, curing, exposure, development, drying and the like of the resin composition. Therefore, not only the working is complicated, but also problems such as complexation of a processing device and increase in manufacturing cost occur. The black matrix is formed from a metal thin film, e.g. thin film of chromium (Cr) or chromium oxide (CrO2) in place of the photosensitive resin composition. In this case, however, a photoresist method must be used for patterning the metal thin film and, therefore, the above-described problems can not be avoided.
Specifically explaining, the above-described black matrix is usually formed through a series of processing steps.
1) A black matrix precursor made of metal, i.e. a thin film of a black matrix forming material is formed on a substrate. For example, a thin film of Cr or a thin film of Cr and CrO2 is formed by a sputtering method.
2) A photosensitive resin composition is coated on the thin film of the black matrix in a predetermined film thickness. Generally, a spin-coating method is used as a coating method.
3) The photosensitive resin composition is cured by prebaking in an oven to obtain a resist film.
4) The resist film is subjected to pattern exposure via a mask with a desired pattern of a black matrix. As an exposure light source, an ultraviolet lamp and the like is used.
5) The unexposed area of the resist film is removed, for example, by developing with an alkali developer.
6) Using, as a mask, the resist film remained without being removed, the exposed area of the underlying thin film of the black matrix precursor is removed by dissolving with an etching solution.
7) The residue on etching is removed by washing. As a result, a black matrix having a desired pattern is obtained.
8) The resist film used as the mask is removed.
Alternatively, the black matrix can also be formed by dispersing the light shielding material such as black pigment in the photosensitive resin composition. In this case, the black matrix precursor, i.e. metal thin film is not used and a glass substrate is used as the substrate. Accordingly, the steps (1) and (6) among the above-described processing steps are omitted and curing is conducted by post baking in place of removal of the resist in the step (8) and the cured resist is remained as it is.
As is understood from the above description, in the method of forming the black matrix by using a photoresist method, six to eight processing steps are generally required, whereby processing devices such as coating device of the resin composition, baking device, exposure device and the like are also required. A method of forming a black matrix of metal according to a deposition method, electroless plating method or the like without using a photoresist method is also considered, however, a problem about the processing step is remained and there is not a merit as compared with the photoresist method.
Under these circumstances, it is desired to provide a method of producing a black matrix, capable of directly forming the black matrix on a substrate without making processing steps and processing devices complex.
By the way, Japanese Unexamined Patent Publication (Kokai) No. 6-347637 cited above discloses a possibility of formation of a partition pattern according to a thermal transfer method, but it is not specifically described. Accordingly, a method of producing a color filter element using a LITI method described in U.S. Pat. No. 5,521,035 will be referred herein with regard to this respect. According to this method, a black matrix can be formed in a desired pattern by transferring a coloring agent from a black donor sheet containing a fluorine surfactant onto a substrate of a color filter element, utilizing thermal transfer due to laser beam. According to the black matrix using the LITL method, satisfactory results can be obtained as compared with a conventional photoresist method, but it is desired to further improve water repellency and oil repellency.
Further, the ink-jet recording method has been utilized in the formation of a luminescent layer made of an organic compound in the production of organic EL elements and devices. For example, International Publication WO98/24271 discloses a method of manufacturing an organic EL element, comprising the steps of: forming pixel electrodes on a transparent substrate; forming on said pixel electrodes by patterning at least one luminescent layer having a certain color and made of an organic compound; and forming a counter electrode opposing the pixel electrodes, wherein the formation of the luminescent layer is performed by means of an ink-jet method.